Diamond Washing Concentrating Machinery

Information on Diamond Washing and Concentrating Machinery.

Diamond Washing and Concentrating Machinery

After the blue ground has been weathered for a sufficient time, it is again loaded into trucks and hauled to the crushing machin ery (Fig.  8).  The first or " comet" crushers reduce the ground so that it will pass into hoppers and thence into revolving cylinders covered with perforated steel plates, having holes i inches in diameter which separate the finely crushed from the coarse pieces.

Pieces larger than i|inches pass out of the end of the cylinders and fall upon a conveyor belt, which takes them to the end of the machine these pieces are mostly waste rock which is found in the blue ground.

The fine ground which passes through the holes in the cylinder, together with a plentiful current of water, flows into the washing pans.  These pans are of iron, E 49 DIAMONDS 14 feet in diameter, furnished with ten arms each having six or seven teeth.  The teeth are so set as to form a spiral, so that when the arms revolve the teeth carry the heavy deposit to the outer rim of the pan, while the lighter material passes towards the centre and is carried from the pan by the flow of water.  The heavy deposit contains the diamonds.  It remains on the bottom of the pan and near its outer rim.

This deposit is drawn off every twelve hours by means of a broad slot in the bottom of the pan.  The average quantity of blue ground passed through each pan is from 400 to 450 loads in ten hours.  The deposit left in each pan after putting the above number of loads through amounts to three or four loads, which go to the pulsator for further concentration.

About 14 per cent of all the ground sent to the depositing floors is too hard to weather, so of late years crushing and con centrating plant has been erected to deal 50 CONCENTRATING MACHINERY effectually with the hard lumps, thus saving the great lock-up of capital consequent on letting them lie on the floor a year or two.

The hard lumps being hauled to the upper part of the machine, are tipped into bins, whence they pass to crushing rollers which so reduce them that they will pass through a ring two inches in diameter.  The coarse powder is screened through revolving cy linders having ^-inch and ij-inch perfora tions.  The stuff passing through the finer holes goes to the finishing mill, while the coarser stuff goes to smaller crushers.

Before the coarse lumps are re-crushed they pass over revolving picking tables, where any specially large diamonds are rescued, thus preventing the risk of breakage.

From the picking tables the ground is scraped automatically into two sets of rolls, and the pulverised product screened again and graded into three sizes.  The finest size, passing a |-inch screen, goes to the washing pans, and the two coarser 5* DIAMONDS sizes to jigs.  Large diamonds which have been separated from their envelope of blue are retained in the jig.  The ground still holding the smaller diamonds passes out of the end of the jig and then through a series of rolls, screens, and jigs until the dia mantiferous gravel is drawn from the bottom jigs into locked trucks running on tramways to the pulsator for further con centration and sorting.

The pulsator is an ingeniously designed but somewhat complicated machine for dealing with the diamantiferous gravel already reduced one hundred times from the blue ground, the pulsator still further concentrating it till the gravel is rich enough to enable the stones to be picked out by hand.  The value of the diamonds in a load of original blue ground being about 305., the gravel sent to the pulsator from the pans, reduced a hundredfold, is worth 150 a load.  Stuff of this value must not be exposed to risk of peculation.

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